An important feature of contemporary cellular wireless networks is an ability to locate the geographical position of a mobile station. Such a feature was initially developed to assist emergency services in locating a mobile station. However, the availability of location information to support emergency services has given rise to the development of many other location-based service (LBS) applications as well.
For example, given the location of a mobile station, an LBS provider (e.g., a wireless cellular carrier or third party) can provide the mobile station user with a weather or traffic report in the user's vicinity, a list of services or establishments in the user's vicinity, navigation instructions for travel from the user's location to another location, or other useful information. As another example, the LBS provider can dispatch emergency assistance to the user at the user's location. And as still another example, the LBS provider can report the mobile station's location to a requesting entity for various purposes, such as to facilitate tracking of the mobile station or of an associated person or object. Other LBS applications exist currently, and more will inevitably be developed in the future as well.
In practice, to facilitate location determination, a wireless carrier may implement a mobile positioning system that is arranged to determine and report mobile station location. Such a system could be invoked when the wireless carrier generates or receives a request to determine the location of a mobile station served by the wireless carrier. For instance, the system could be invoked when the wireless carrier receives a request for location of a mobile station from a third party LBS provider (such as an Internet application from which a user of the mobile station has requested location-based information). The system could then determine the mobile station's location and report the determined location to the requesting LBS provider. Likewise, the system could be invoked when the mobile station places an emergency (e.g., 911) call through the wireless carrier network. In that case, the system could be invoked during setup of the emergency call, and the system could report to an emergency services provider (e.g., public safety answering point) the determined location so as to enable emergency response.
A mobile positioning system may be configured to determine the location of a mobile station by using global positioning satellite signals received by the mobile station. To do this in practice, the mobile positioning system may receive an identifier of the base station that is currently serving the mobile station and may use that base station identifier (BSID) as a key to perform a lookup in base station almanac data, so as to obtain satellite assistance data that identifies satellites in the sky over that particular base station. The mobile positioning system may then transmit that obtained satellite assistance data to the mobile station, and the mobile station may use the data as a basis to tune to the indicated satellites and to obtain pertinent satellite signal information. The mobile station may then send that obtained satellite signal information to the mobile positioning system, and the mobile positioning system may use the information as a basis to determine the mobile station's location.